One suspect uses a black box to break into a car while another hovers nearby in this video from Long Beach, Calif., police / Long Beach Police

by Chris Woodyard, USA TODAY

by Chris Woodyard, USA TODAY

Auto break-in specialists have gone high-tech -- and stopping thieves has become much harder.

More thieves around the country use mysterious hand-held devices that can unlock a car's doors, CNN reports. One recent case involving these "black boxes," caught on tape, came in Chicago.

Last April, police in Long Beach, Calif., asked for the public's help in trying to nab three suspects wanted in connection with a series of auto burglaries. They used "unknown technology" to gain entry to cars without the keys.

"This is a situation where technology is working against us, making our job much more challenging at a time where resources are already strained," said Long Beach Police Chief Jim McDonnell in a statement at the time. "Just as law enforcement tactics evolve, so does the criminal element's -- and we need the community's involvement more so than ever."

The trio are seen on a surveillance tape. Two suspects are seen walking up to four different vehicles -- two on the street and two in a driveway, according to police. Another hovers in the background.

To protect yourself, police say make sure valuables are removed from cars when they are parked and that there is not a "valet key" left in the car. They also recommend installing security cameras around a home.